<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div id="app"></div>
  <template id="my-app">
    <h2>今天温度：{{temp}} 度</h2>
    <h3>建议穿：{{suggestion}}</h3>

    <button @click="add">+</button>
    <button @click="minus">-</button>
  </template>


  <script src="https://unpkg.com/vue@3/dist/vue.global.js"></script>
  <script>
    const App = {
      template: '#my-app',
      data() {
        return {
          temp: 10,
          // suggestion: '夹克'
        }
      },
      computed: {
        suggestion() { // 响应式执行，当它依赖的数据源发生变成时
          let res = '夹克'
          if (this.temp >= 20) {
            res = '短袖'
          } else if (this.temp <= 0) {
            res = '羽绒服'
          } else {
            res = '夹克'
          }
          return res
        }
      },
      methods: {
        add() {
          this.temp += 5
          // if (this.temp >= 20) {
          //   this.suggestion = '短袖'
          // } else if (this.temp <= 0) {
          //   this.suggestion = '羽绒服'
          // } else {
          //   this.suggestion = '夹克'
          // }
        },
        minus() {
          this.temp -= 5
          // if (this.temp >= 20) {
          //   this.suggestion = '短袖'
          // } else if (this.temp <= 0) {
          //   this.suggestion = '羽绒服'
          // } else {
          //   this.suggestion = '夹克'
          // }
        }
      }
    }
    Vue.createApp(App).mount('#app')
  </script>
</body>
</html>